The National Stock Exchange of India (NSE) has filed its Draft Red Herring Prospectus (DRHP) with market regulator SEBI for its long-awaited initial public offering (IPO), setting the stage for one of the largest and most closely watched listings in the history of India's capital markets. With NSE's valuation in the unlisted market hovering around Rs 5 lakh crore, market estimates suggest the IPO could be sized at roughly Rs 30,000 crore, making it one of the biggest public offerings in India.